Biopolymer-Based Minimal Formulations Boost Viability and Metabolic Functionality of Probiotics <i>Lactobacillus rhamnosus</i> GG through Gastrointestinal Passage

The delivery of probiotic microorganisms as food additives via oral administration is a straightforward strategy to improve the intestinal microbiota. To protect probiotics from the harsh environments in the stomach and small intestine, it is necessary to formulate them in biocompatible carriers, which finally release them in the ileum and colon without losing their viability and functions. Despite major progresses in various polymer-based formulations, many of them are highly heterogeneous and too large in size and hence often “felt” by the tongue. In this study, we established a new formulation for probiotics Lactobacillus rhamnosus GG (LGG) and systematically correlated the physicochemical properties of formulations with the functions of probiotics after the delivery to different gastrointestinal compartments. By reducing the stirring speed by 1 order of magnitude during the emulsification of polyalginate in the presence of xanthan gum, we fabricated microparticles with a size well below the limit of human oral sensory systems. To improve the chemical stability, we deposited chitosan and polyalginate layers on particle surfaces and found that the deposition of a 20 nm-thick layer is already sufficient to perfectly sustain the viability of all LGG. Compared to free LGG, the colony-forming units of LGG in these formulations were by factors of 10 7 larger in stomach fluid and 10 4 larger in small intestine fluid. The metabolic functionality of LGG in polymer formulations was assessed by measuring the amount of lactate produced by LGG in a human gastrointestinal simulator, showing 5 orders of magnitude larger values compared to free LGG. The obtained results have demonstrated that the minimal formulation of LGG established here boosts not only the viability but also the metabolic functionality of probiotics throughout oral uptake, passage through the gastrointestinal tract, and delivery to the ileum and colon.